LMR systems are wireless communications systems generally intended for use by terrestrial users in vehicles or on foot. Such systems are often used by emergency first responder organizations such as police, fire and ambulance services, public works organizations, dispatched services such as taxis, and companies with large vehicle fleets or numerous field staff. LMR systems are often independent, but can be connected to other fixed systems such as the public switched telephone network (PSTN) or cellular networks.
Radio over Internet Protocol (RoIP) is similar to VoIP, but augments two-way radio communications rather than telephone calls. With RoIP, at least one node of a network is a radio (or a radio with an IP interface device) connected via IP to other nodes in the radio network. The other nodes can be two-way radios, but can also be dispatch consoles, either traditional (hardware) or modern (software on a PC), plain old telephone service (POTS) telephones, softphone applications running on a computer such a smartphone or some other communications device accessible over IP. RoIP has been deployed over private networks as well as the Internet. RoIP has shown to be useful in LMR systems used by public safety departments and utility fleets spread over a broad geographic area. Like other centralized radio systems such as trunked radio systems, issues of delay or latency and reliance on centralized infrastructure can be impediments to adoption by public safety agencies.
Examples of previous attempts to integrate LMR with VoIP include U.S. Pat. No. 8,145,262 issued to Martinez that claims to disclose a multimode LMR and a method of communicating LMR content using an LMR device. The Martinez LMR system includes an LMR communication portion and a cellular data network communication portion.
U.S. Pat. No. 8,169,983 issued to Janky claims to disclose a transcoder architecture and method for transcoding in LMR systems. The Janky LMR system includes a first communication site configured to communicate using a first LMR communication protocol and a second communication site configured to communicate using a second LMR communication protocol. The Janky LMR system further includes a transcoder configured to receive LMR content from the first communication site communicated using the first LMR communication protocol and digitally converts the LMR content to the second LMR communication protocol to be communicated to the second communication site.
U.S. Pat. No. 8,634,799 issued to Economy claims to disclose an incident commander computing device that dynamically reconfigures subscriber unit usage of radio access networks by first identifying, based at least on a type of incident occurring within a particular geographic area, a first incident response group having a first higher priority for responding to the incident and a second incident response group having a second lower priority for responding to the incident, then identifying a first higher priority radio access network having a sufficient coverage level across the particular geographic area and a second lower priority radio access network having a sufficient coverage level across the particular geographic area, and finally assigning the first incident response group to the first higher priority radio access network and assigning the second incident response group to the second lower priority radio access network.
U.S. Pat. No. 8,676,243 issued to Blanco claims to disclose a communication system that provides dual-watch and multi-watch capability for group PTT services where incoming PTT calls are prioritized and played out in accordance with prioritization protocols. In the Blanco system, a user of multiple communication devices can hear received audio traffic being played out in accordance with the priority assigned to the group call and the priority assigned to the communication device, and numerous calls can be simultaneously received and managed.